Three sisters are torn apart by the chaos of World War II, and their fight for peace may be the only way to find each other again.

In December 1941, Amelie and Mireille, evacuated from London, are now actively contributing to the British war effort. Amelie serves as a nurse, tending to wounded soldiers, while Mireille joins the Air Force. Both are driven by a desire to end the war, but the memory of their third sister, lost at the war's outset, continues to haunt them. Mireille's recruitment into a special forces role behind enemy lines in France offers a dangerous path, but also the potential for a reunion once the conflict concludes.

Menrva reader comments indicate that 'The Lost Orphan' is a highly engaging and emotional read, with reviewers frequently mentioning their inability to put the book down and experiencing significant emotional responses, including tears at the conclusion. The characters are praised for their bravery and determination, making them feel like 'old friends' to the readers. The plot is described as pacy and full of twists and turns, leading to a compelling narrative that keeps readers invested throughout. The author's skill in crafting plot and setting is noted, contributing to a story that moves along briskly and leaves a lasting impression.